The present invention relates to the prevention of failure of tomato-based sauces during storage, e.g., frozen storage. During storage of tomato-based sauces, they tend to change color from red to orange, develop off-flavors and lose flavor strength even when the food product is in frozen distribution. This was particularly noted when the tomato-based sauce was in contact with cheese, for example, when the sauce is on a pizza.
Although not wishing to be bound by the following theory, the following explanation is provided. It is believed that the major failure mechanism of tomato-based sauces is due to an oxidation reaction in the sauce which occurs even in frozen distribution because of the depressed freezing point of the sauce. For pizza sauce, the sauce contains a high level of tomato paste. Characteristic color and flavor of the tomato product is due to the presence of lipid soluble pigments called lycopenes, a type of beta carotenoid pigment. These pigments are very sensitive to oxidation. In the presence of oxygen, the pigments oxidize resulting in loss of color, flavor and development of off-flavors. The pigment molecule has several double-bonds and when oxygen is present, it combines with the double-bonds resulting in the product having oxidative decomposition which decomposition produces hydroperoxides, carbonyl compounds and other volatile and malodorous compounds.
Oxygen can occur in the sauce by being mixed during a mixing process and can also be in the surrounding atmosphere inside a package. If the tomato-based sauce is canned where all the dissolved oxygen is removed and the container is impervious to oxygen, then the oxidative failure does not occur even after a shelf life of several years.
When tomato sauce is used on other products, for example, frozen pizza, there is essentially no protection of the product from oxygen at any time during its processing and storage, thus providing an opportunity for sauce failure.
For example, when pizza sauce is made, a mixture of tomato paste, water, spices, sugar, salt, oil and thickeners is mixed at high shear and cold temperatures. During mixing, atmospheric oxygen is dissolved in the sauce. After the sauce has been applied to the pizza crust, and other topping ingredients added, the pizza is frozen and packaged. The packaging consists of the plastic film overwrap and a carton. Both of these packaging components offer physical protection but provide little barrier to atmospheric oxygen during product distribution and storage. To eliminate dissolved oxygen during sauce mixing and application to the crust would require high-cost, sophisticated equipment. Further, to provide an effective oxygen barrier package would require high-cost packaging equipment and materials.
Consumer testing indicates that the major problem with frozen pizzas is degradation of sauce with age. It has been a long-felt need in the pizza industry to provide a stable tomato sauce which does not degrade with age to prevent the above discussed problems. The present invention satisfies that need by providing a more stable sauce without the necessity of expensive packaging and/or equipment.
It is an object of the present invention to provide a tomato sauce which is stable during distribution and storage of the sauce product.
It is another object of the present invention to provide a tomato-based sauce which is resistant to failure with time and is inexpensive and safe.
It is a still further object of the present invention to provide a tomato-based sauce which is stable when in contact with other food products, for example, cheese.